The ECM will make decisions that are based on input data information and programming parameters that have been flashed to the ECM memory. After the ECM receives the input information, the ECM determines the correct response and sends an output signal to the appropriate device. The internal input circuits and the internal output circuits of the ECM are connected to the machine wiring harness by two contact connectors (J1 and J2).
Note: The ECM is not serviceable. If the ECM is damaged, the ECM must be replaced. The ECM failure is unlikely. If the ECM failure is suspected, contact the Technical Communicator at a local dealership for possible consultation with AVSpare before replacing the ECM. Replace the ECM only after all of the other possible causes of a particular problem have been investigated.
To aid in diagnostics of some electrical circuits monitored by the ECM, an internal "pull up voltage" is connected to ECM switch-to-ground and sensor signal input contacts. An above normal voltage is internally connected to the ECM signal input circuit through a resistor.
During normal operation, the switch or sensor signal will hold the circuit low or at a certain signal amplitude, however, circuit conditions such as a loss of power to the component, a disconnection, or an open circuit will allow the circuit to be pulled high by the ECM pull up voltage. The pull up voltage will result in an above normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 3 (voltage above normal) diagnostic code for the affected circuit.
The types of ECM input circuits that have pull up voltage present are:
- Pulse Width Modulated (PWM) sensor input circuits
- Switch to ground switch input circuits
- Active analog (voltage) input signal circuits
- Passive analog (resistance) input signal circuits
To aid in diagnostics of electrical circuits that are controlled by the ECM, an internal “"pull down voltage"” is connected to ECM switch to battery type input circuits.
During normal operation, the switch contacts that are allowing the connection to a voltage source will hold the circuit high. When circuit conditions such as a loss of power to the switch supply voltage, a disconnection in the switch circuit or an open circuit will allow the circuit to be pulled low by the ECM pull down voltage. The pull-down voltage will result in a below normal voltage condition at the ECM contact. As a result, the ECM will activate an FMI 04 (voltage below normal) diagnostic code for the affected circuit.
The machine has several different types of input devices. The ECM receives machine status information from the input devices and determines the correct output action that is needed to control machine operations based on memory and software parameters. The machine utilizes the following types of inputs: switch type and sensor type.
Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open signal, a grounded signal and + battery signal.
Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to the ECM can be one of several different types of electrical signals such as: pulse width modulated (PWM) signals, voltage signals and frequency input signals. Each possible input to the Transmission ECM and the Implement ECM are listed in the tables for the 70-pin connectors.
The ECM sends electrical signals through the outputs. The outputs can create an action or the outputs can provide information to the ECM. The ECM can send output signals to the system components in one of several different electrical signal types such as: sourcing driver outputs, sinking driver outputs, sensor power supply outputs and data link outputs. The possible outputs for the Machine ECM are listed in the tables for the 70 pin connectors.
Communication between the Transmission ECM, Implement ECM, and the other control modules on the machine is conducted over data link circuits. The data link circuits allow the sharing of information with other electronic control modules. The data link circuits are bidirectional. The data link circuit allows each ECM to send information and to receive information.
The ECM supports two types of data link systems.
- Cat Data Link
- SAE J1939 Data Link
The two types of data links are the main structure for communication between all of the control modules on the machine. More than one CAN data link system can be present on a machine. Dedicated CAN data link circuits can be used for communication between specific controls on the machine.
Communication between the Transmission ECM, Implement ECM, and the other control modules on the machine are conducted over the J1939 Data Link circuit. The ECM modules use the Cat® Data Link to send and receive information from the Cat Electronic Technician (ET) Service Tool.
A module identifier (MID) is assigned to each ECM on a machine. The MID for the Transmission ECM is 81.The MID for the Implement ECM is 82.
Note: All diagnostic codes for the components in the machine control system are activated by the Transmission ECM (MID 81) or the Implement ECM (MID 82).
Note: The following tables list the connections for the Transmission ECM and Implement ECM. Depending on the attachments that are installed on your machine, some of the listed circuits may not be present.
| Contact Description J1(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Key Switch On | Key Switch Input |
| 2 | TC Output Speed Sensor + | Differential Speed Input (+) |
| 3 | TC Output Speed Sensor - | Differential Speed Input (-) |
| 4 | TC Output Speed Sensor + | Differential Speed Input (+) |
| 5 | TC Output Speed Sensor - | Differential Speed Input (-) |
| 10 | CDL High | Cat Data Link (+) |
| 12 | Backup Alarm | Sourcing Driver Output |
| 13 | Battery Negative | Battery Return |
| 15 | Trans Input Speed Sensor + | Differential Speed Input (+) |
| 16 | Trans Input Speed Sensor - | Differential Speed Input (-) |
| 20 | CDL Low | Cat Data Link (-) |
| 23 | Battery Negative | Battery Return |
| 27 | Location Code 2 | Switch to Ground Input |
| 30 | Torque Converter Oil Temperature | Analog Input |
| 31 | Battery Positive | Battery Power Input |
| 32 | Location Code (Grounded) | Switch to Ground Input |
| 33 | Steering/ Trans Lock (N/C) | Switch to Ground Input |
| 34 | Steering/ Trans Lock (N/O) | Switch to Ground Input |
| 36 | Autolube Pump Pressure Sensor | Analog Input |
| 37 | Autolube Grease Pressure Sensor | Analog Input |
| 38 | Battery Positive | Battery Power Input |
| 39 | Battery Positive | Battery Power Input |
| 40 | Upshift Switch (N/C) | Switch to Ground Input |
| 41 | Upshift Switch (N/O) | Switch to Ground Input |
| 42 | Downshift Switch (N/C) | Switch to Ground Input |
| 43 | Downshift Switch (N/O) | Switch to Ground Input |
| 44 | 8V Supply | Sensor Power Output |
| 45 | 8V Return | Sensor Power Return |
| 48 | Trans Solenoid 6 (Speed 1) | Sourcing Driver Output |
| 49 | Trans Solenoid 4 (Speed 3) | Sourcing Driver Output |
| 50 | PWM Dr 1-4 Return | Sourcing Driver Return |
| 51 | Trans Solenoid 5 (Speed 2) | Sourcing Driver Output |
| 53 | Fuel Level Sender | Analog Input |
| 55 | PWM Dr 9-12 Return | Sourcing Driver Return |
| 56 | 10V Return | Sensor Power Return |
| 57 | Battery Negative | Battery Return |
| 60 | PWM Dr 5-8 Return | Sourcing Driver Return |
| 62 | Trans Solenoid 2 (Forward) | Sourcing Driver Output |
| 63 | Trans Oil Filter Bypass Sw | Switch to Ground Input |
| 65 | Trans Solenoid 1 (Reverse) | Sourcing Driver Output |
| 66 | Trans Solenoid 3 (Speed 4) | Sourcing Driver Output |
| 69 | 10V Supply | Sensor Power Output |
| 70 | Battery Negative | Battery Return |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Keyswitch Start | Switch to Battery Input |
| 2 | Axle Oil Cooler Bypass Solenoid | Sourcing Driver Output |
| 3 | Main Relay | Sourcing Driver Output |
| 4 | 2A On/Off Return 1-3 | Sourcing Driver Return |
| 5 | Park Brake Solenoid | Sourcing Driver Output |
| 6 | Machine Power Distribution Relay | Sourcing Driver Output |
| 7 | Start Relay | Sourcing Driver Output |
| 8 | 2A On/Off Return 4-5 | Sourcing Driver Return |
| 10 | Heated Mirror Relay | Sinking Driver Output |
| 11 | Machine Feature Alarm | Sinking Driver Output |
| 12 | Operator Seat Belt Beacon Relay | Sinking Driver Output |
| 13 | Bumper Transmission Lockout Led | Sinking Driver Output |
| 17 | Transmission Oil Temperature Sensor | PWM Input |
| 19 | Backlight Dimmer #1 | Sinking Driver Output |
| 21 | Backlight Dimmer #2 | Sinking Driver Output |
| 23 | Direction Switch (Neutral) | Switch to Ground Input |
| 28 | Direction Switch (Reverse) | Switch to Ground Input |
| 32 | Service Brake Pressure Sensor | PWM Input |
| 33 | Park Brake Oil Pressure Sensor | PWM Input |
| 34 | Brake Charge Pressure Sensor | PWM Input |
| 35 | Torque Converter Pedal Position Sensor | PWM Input |
| 37 | Park Brake Operator Switch (N/O) | Switch to Ground Input |
| 38 | Park Brake Operator Switch (N/C 1) | Switch to Ground Input |
| 39 | Park Brake Operator Switch (N/C 2) | Switch to Ground Input |
| 44 | Bumper Transmission Lockout Sw (N/C) | Switch to Ground Input |
| 47 | Bumper Transmission Lockout Sw (N/O) | Switch to Ground Input |
| 48 | Direction Switch (Forward) | PWM Input |
| 49 | Front Axle Oil Temperature Sensor | PWM Input |
| 50 | Rear Axle Oil Temperature Sensor | PWM Input |
| 52 | Operator Seat Belt Switch (N/O) | Switch to Ground Input |
| 53 | Operator Seat Belt Switch (N/C) | Switch to Ground Input |
| 54 | LH Armrest Position Sw N/O | Switch to Ground Input |
| 55 | LH Armrest Position Sw N/C | Switch to Ground Input |
| 56 | CAN A High | CAN Data Link (+) |
| 64 | CAN B High | CAN Data Link (+) |
| 65 | CAN B Low | CAN Data Link (-) |
| 67 | CAN A High | CAN Data Link (+) |
| 68 | CAN A Low | CAN Data Link (-) |
| 70 | CAN A Low | CAN Data Link (-) |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description J1(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Keyswitch | Key Switch Input |
| 10 | CDL High | Cat Data Link (+) |
| 12 | Implement Pilot Supply Solenoid | Sourcing Driver Output |
| 13 | Battery Negative | Battery Return |
| 20 | CDL Low | Cat Data Link (-) |
| 21 | 5V Return | Sensor Power Return |
| 22 | Hydraulic Oil Temperature | Analog Input |
| 23 | Battery Negative | Battery Return |
| 28 | Location Code 4 (Grounded) | Switch to Ground Input |
| 29 | Cab Air Temperature | Analog Input |
| 30 | Air Condition Evaporator Coil Temp | Analog Input |
| 31 | Battery Positive | Battery Power Input |
| 32 | Location Code Enable (Grounded) | Switch to Ground Input |
| 33 | Implement Lockout Switch (N/O) | Switch to Ground Input |
| 34 | Implement Lockout Switch (N/C) | Switch to Ground Input |
| 36 | Operator Requested Cab Air Temp | Analog Input |
| 37 | Car Blower Speed Control Position | Analog Input |
| 38 | Battery Positive | Battery Power Input |
| 39 | Battery Positive | Battery Power Input |
| 41 | Joystick Trigger (N/O) | Switch to Ground Input |
| 42 | Joystick Trigger (N/C) | Switch to Ground Input |
| 44 | 8V Sensor Power | Sensor Power Output |
| 45 | 8V Sensor Return | Sensor Power Return |
| 48 | Raise Solenoid | Sourcing Driver Output |
| 49 | Lower Solenoid | Sourcing Driver Output |
| 50 | PWM Dr 1-4 Return | Sourcing Driver Return |
| 51 | L Tilt Cyl Extend/Tilt L Solenoid | Sourcing Driver Output |
| 52 | L Tilt Cyl Retract/Tilt R Solenoid | Sourcing Driver Output |
| 53 | Cab Ventilation Duct Air Temp | Analog Input |
| 55 | PWM Dr 9-12 Return | Sourcing Driver Return |
| 56 | 10V Sensor Return | Sensor Power Return |
| 57 | Battery Negative | Battery Return |
| 58 | 3rd Function Rearward Solenoid | Sourcing Driver Output |
| 59 | 3rd Function Forward Solenoid | Sourcing Driver Output |
| 60 | PWM Dr 5-8 Return | Sourcing Driver Return |
| 61 | Rh Tilt Cyl Extend Solenoid | Sourcing Driver Output |
| 62 | Rh Tilt Cyl Retract Solenoid | Sourcing Driver Output |
| 65 | Variable Implement Pump Solenoid | Sourcing Driver Output |
| 66 | Steering Excess Flow Solenoid | Sourcing Driver Output |
| 69 | 10V Sensor Power | Sensor Power Output |
| 70 | Battery Negative | Battery Return |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |
| Contact Description J2(1) | ||
|---|---|---|
| No.(2) | Function | Type |
| 1 | Battery Positive | Switch to Battery Input/ |
| 3 | AC Compressor Clutch Solenoid1 | Sourcing Driver Output |
| 4 | 2A On/Off Return 1-3 | Sourcing Driver Return |
| 5 | Lift Float Solenoid | Sourcing Driver Output |
| 6 | Ride Control Activation Solenoid | Sourcing Driver Output |
| 7 | Ride control Balance Solenoid | Sourcing Driver Output |
| 8 | 2A On/Off Return 4-5 | Sourcing Driver Return |
| 9 | Operator Horn Relay | Sinking Driver Output |
| 13 | AC Condenser Cooling Fan Relay | Sinking Driver Output |
| 15 | Lift Cylinder Position Sensor | PWM Input |
| 17 | Lift Cylinder He Pressure | PWM Input |
| 18 | Lift Cylinder Re Pressure | PWM Input |
| 19 | Cab Blower Motor Command | Sinking Driver Output |
| 21 | Cab Air Heater Engine Coolant Actuator | Sinking Driver Output |
| 23 | Payload Store Switch | Switch to Ground Input |
| 24 | Joystick Lift Position Sensor | PWM Input |
| 25 | Joystick Tilt Position Sensor | PWM Input |
| 26 | Joystick Thumb Rocker Position Sensor | PWM Input |
| 28 | Joystick Pushbutton #1 (N/O) | Switch to Ground Input |
| 29 | Joystick Pushbutton #1 (N/C) | Switch to Ground Input |
| 30 | Joystick Pushbutton #2 (N/O) | Switch to Ground Input |
| 31 | Joystick Pushbutton #2 (N/C) | Switch to Ground Input |
| 32 | Lift Linkage Position Sensor | PWM Input |
| 33 | Tilt Linkage Position Sensor | PWM Input |
| 36 | Fan Return Filter Bypass Switch | Switch to Ground Input |
| 37 | Pilot Filter Bypass Switch | Switch to Ground Input |
| 38 | Case Drain Filter Bypass Switch | Switch to Ground Input |
| 40 | Hydraulic Press | PWM Input |
| 46 | 3rd Function Lockout Sw (N/O) | Switch to Ground Input |
| 47 | 3rd Function Lockout Sw (N/C) | Switch to Ground Input |
| 48 | Steer Press Red | PWM Input |
| 51 | Implement Pump Pressure Sensor | PWM Input |
| 56 | CAN A High | CAN Data Link (+) |
| 60 | Cab Air Temp Control Sw (On) | Switch to Ground Input |
| 61 | Cab Air Temp Control Sw (Auto) | Switch to Ground Input |
| 62 | AC Refrigerant Monitoring Circuit | Switch to Ground Input |
| 64 | CAN B High | CAN Data Link (+) |
| 65 | CAN B Low | CAN Data Link (-) |
| 67 | CAN A High | CAN Data Link (+) |
| 68 | CAN A Low | CAN Data Link (-) |
| 70 | CAN A Low | CAN Data Link (-) |
| (1) | The ECM responds to an active input only when all the necessary conditions are satisfied. |
| (2) | The connector contacts that are not listed are not used. |